>By the way, wouldn't it be possible to calculate in advance which detail record will be the last to fit on the current page

When this detail/child record has been reached, report variables should be set to indicate that there are pending detail records and which detail record was the last printed and from which extended detail band. Printing of detail records should then stop letting the report footer do its' job. When coming around past the page header again, the report writer should not be allowed to skip to the next record in the parent table, but be forced to print it again with the remaining detail records.